I'm gonna try to explain each dimension and its important role when it comes to simpvp and in order for which would be affected first.
Firstly the end. When it comes to end terrain there is no legitimate way to follow any sort of end trails, even if you found a few raided end cities. Following a line of raided end cities is near impossible if the raider changed up their pattern in flying i.e. flew in a straight line, (obvious pattern to follow,) but then suddenly turned and you've lost it. It would take extensive amounts of graphing or mapping (Xareos world map is gone and there is no way to map now.)
Huge time waste and really not worth the effort. Also important to this and other dimensions; updates in terrain. There has been nothing said by Mojang about an end update that would make keeping end chunks important to keep in the sake of trail following. What can be said is chunks loaded for less than a minute, more or less, are completely useless and I think should be cleaned up.
Next is the nether. If any nether would to be deleted it should only be chunks loaded post 1.16. Following loaded lava in the nether is possible with a repeating pattern such as a straight point from A. to B. If the flyer constantly changed up their direction its nearly impossible and quite a large frustration. Once again, large amounts of documented graphing or mapping would be to be done to follow these trails, not to mention you yourself are loading lava too and in some cases you can confuse yourself in your own loaded lava if you're struggling to find where the trail turned. So, these post 1.16 nether chunks really serve no purpose, and it was just recently updated, so I don't see a update coming to it all in the near future.
Overworld is the most important when it comes to not deleting any chunks and if any were either post 1.14 or post 1.18 (will discuss more). Once the server updates to 1.18 following chunk trails should be very easy, but I'm not sure because of the way they made the border blend so well. Same idea with patterns, if the person flew in a straight pattern and you notice the biome blends the whole time, you got an obvious trail. If they sporadically flew, then it's just a little bit more frustrating like following trails from 1.7 to 1.12 and you trying to find where it picks up again. A very strong point that I think is important to all of this is we don't want to isolate bases making them too safe and giving others a disadvantage. Deleting trails to the bases basically gives them "tp'd" like conditions, as if just an admin did /tp'd to them. I think its important we keep that balance and make sure we all have equal advantage. That there is the main reason why I'm against deleting any overworld chunks for now. Now, 1.18, once the server updates it's likely many people will be loading new chunks, and with that will come larger server files. Along with extra space possibly saved by cleaning up the end, it can help us survive into 1.18 for a little while. Something that I would be for and could be done in the future is deleting any chunks made in 1.18 or in the future. Deleting 1.18 chunks really has no effect just like the end, it doesn't put anyone at a disadvantage, nor will it probably ever update again in the near future. (Basically suggesting regular basis clean ups in the future once the server updates)